Ultrastructural and morphometric alterations in bone marrow stromal tissue after 7 Gy irradiation.

To evaluate the response of marrow stroma to 7 Gy irradiation, femoral bone marrow was fixed by vascular perfusion (so as to avoid the artificial destruction of sinus endothelia), and was examined using light and electron microscopy with morphometric methods. The radiation caused a marked decrease in hematopoietic cell number (NHC) within 3 days post-irradiation, followed by total recovery of hematopoiesis, which occurred gradually over 28 days. An increased number of fat cells was seen by 7 days. During the whole course of hypoplasia and recovery, the continuity of sinus wall, three-dimensional reticular mesh work in hematopoietic parenchyma, gap junctions (GJ) between stromal cells, the adventitial cell cover of sinus wall (ACC), and the stromal cell numbers of reticular cells (RC), sinus endothelia (SE), and macrophages (MP) were maintained. The cellularity of stromal components of RC, SE, and MP seemed passively increased in contrast to a reduction in numbers of NHC. A similar tendency was observed (1) between NHC and ACC and (2) between GJ and the cellularity of fat cells, which had a statistical significant correlation (p less than 0.05; t-test). The mechanism of radio resistance in bone marrow stroma and the possible functional adaptation and cellular coordination after irradiation are discussed.